Individual differences in sensorimotor skills among musicians

Motor learning is regulated by postnatal GDNF levels in Purkinje cells

Purkinje cells (PCs), the sole output neurons of the cerebellar cortex, are crucial for cerebellum-dependent motor learning. In cerebellar ataxia, reduction in motor function and learning associates with decreased spontaneous activity of PCs. Thus, understanding what molecules regulate PCs activity is important. Previously, we demonstrated that a ubiquitous 2-fold increase of endogenous glial cell line-derived neurotrophic factor (GDNF) improves motor function in adult mice and motor learning and coordination in aged mice. However, since GDNF impacts many organ systems the underlying mechanism remained elusive. Here we utilize GDNF Hypermorphic, conditional GDNF Hypermorphic and conditional knock-out mouse models to reveal that up to a 2-fold increase in endogenous GDNF, specifically in PCs postnatally, is sufficient to enhance motor learning. We find that improved motor learning associates with increased glutamatergic input to PCs and with elevated spontaneous firing rate of PCs, opposite to cerebellar ataxia where reduction in motor function and learning associates with decreased spontaneous activity of PCs. Analysis of the human cerebellum revealed that normal interindividual variation in GDNF expression levels falls in the same variation range as studied in the mouse models, suggesting that interindividual variation in PC GDNF levels may contribute to interindividual variation in PC function. Collectively, our findings reveal how a relatively small change in postnatal GDNF expression level within the physiological range in one cell type, the PCs, affects motor learning. Thus, drugs enhancing postnatal GDNF expression in PCs or cerebellar GDNF signaling may have potential in treating cerebellar ataxias, making an interesting topic for future studies.

Ethnokinesiology: towards a neuromechanical understanding of cultural differences in movement

Each individual's movements are sculpted by constant interactions between sensorimotor and sociocultural factors. A theoretical framework grounded in motor control mechanisms articulating how sociocultural and biological signals converge to shape movement is currently missing. Here, we propose a framework for the emerging field of ethnokinesiology aiming to provide a conceptual space and vocabulary to help bring together researchers at this intersection. We offer a first-level schema for generating and testing hypotheses about cultural differences in movement to bridge gaps between the rich observations of cross-cultural movement variations and neurophysiological and biomechanical accounts of movement. We explicitly dissociate two interacting feedback loops that determine culturally relevant movement: one governing sensorimotor tasks regulated by neural signals internal to the body, the other governing ecological tasks generated through actions in the environment producing ecological consequences. A key idea is the emergence of individual-specific and culturally influenced motor concepts in the nervous system, low-dimensional functional mappings between sensorimotor and ecological task spaces. Motor accents arise from perceived differences in motor concept topologies across cultural contexts. We apply the framework to three examples: speech, gait and grasp. Finally, we discuss how ethnokinesiological studies may inform personalized motor skill training and rehabilitation, and challenges moving forward.This article is part of the theme issue 'Minds in movement: embodied cognition in the age of artificial intelligence'.

Active perceptual learning involves motor exploration and adaptation of predictive sensory integration

Our ability to perceive both externally generated and self-generated sensory stimuli can be enhanced through training, known as passive and active perceptual learning (APL). Here, we sought to explore the mechanisms underlying APL by using active haptic training (AHT), which has been demonstrated to enhance the somatosensory perception of a finger in a trained motor skill. In total 120 pianists participated in this study. First, AHT reorganized the muscular coordination during the piano keystroke. Second, AHT increased the relative reliance on afferent sensory information relative to predicted one, in contrast to no increment of overall perceptual sensitivity. Finally, AHT improved feedback movement control of keystrokes. These results suggest that APL involves active exploration and adaptation of predictive sensory integration, which underlies the co-enhancement of active perception and feedback control of movements of well-trained individuals.

The plyometric activity as a conditioning to enhance strength and precision of the finger movements in pianists

Stability of timing and force production in repetitive movements characterizes skillful motor behaviors such as surgery and playing musical instruments. However, even trained individuals such as musicians undergo further extensive training for the improvement of these skills. Previous studies that investigated the lower extremity movements such as jumping and sprinting demonstrated enhancement of the maximum force and rate of force development immediately after the plyometric exercises. However, it remains unknown whether the plyometric exercises enhance the stability of timing and force production of the dexterous finger movements in trained individuals. Here we address this issue by examining the effects of plyometric exercise specialized for finger movements on piano performance. We compared the training-related changes in the piano-key motion and several physiological features of the finger muscles (e.g., electromyography, rate of force development, and muscle temperature) by well-trained pianists. The conditioning demonstrated a decrease of the variation in timing and velocity of successive keystrokes, along with a concomitant increase in the rate of force development of the four fingers, but not the thumb, although there was no change in the finger muscular activities through the activity. By contrast, such a conditioning effect was not evident following a conventional repetitive piano practice. In addition, a significant increase in the forearm muscle temperature was observed specifically through performing the plyometric exercise with the fingers, implying its association with improved performance. These results indicate effectiveness of the plyometric exercises for improvement of strength, precision, and physiological efficiency of the finger movements even in expert pianists, which implicates that ways of practicing play a key role in enhancing experts' expertise.

Expertise- and Tempo-Related Performance Differences in Unimanual Drumming

BACKGROUND

High-speed drumming requires precise control over the timing, velocity, and magnitude of striking movements.

AIM

To examine effects of tempo and expertise on unaccented repetitive drumming performance using 3D motion capture.

METHODS

Expert and amateur drummers performed unimanual, unaccented, repetitive drum strikes, using their dominant right hand, at five different tempi. Performance was examined with regard to timing variability, striking velocity variability, the ability to match the prescribed tempo, and additional variables.

RESULTS

Permutated multivariate analysis of variance (PERMANOVA) revealed significant main effects of tempo (p < .001) and expertise (p <.001) on timing variability and striking velocity variability; low timing variability and low striking velocity variability were associated with low/medium tempo as well as with increased expertise. Individually, improved precision appeared across an optimum tempo range. Precision was poorest at maximum tempo (400 hits per minute) for precision variables.

CONCLUSIONS

Expert drummers demonstrated greater precision and consistency than amateurs. Findings indicate an optimum tempo range that extends with increased expertise.

Overcoming the ceiling effects of experts' motor expertise through active haptic training

One of the most challenging issues among experts is how to improve motor skills that have already been highly trained. Recent studies have proposed importance of both genetic predisposition and accumulated amount of practice for standing at the top of fields of sports and performing arts. In contrast to the two factors, what is unexplored is how one practices impacts on experts' expertise. Here, we show that training of active somatosensory function (active haptic training) enhances precise force control in the keystrokes and somatosensory functions specifically of expert pianists, but not of untrained individuals. By contrast, training that merely repeats the task with provision of error feedback, which is a typical training method, failed to improve the force control in the experts, but not in the untrained. These findings provide evidence that the limit of highly trained motor skills could be overcome by optimizing training methods.

Neuromuscular and biomechanical functions subserving finger dexterity in musicians

Exceptional finger dexterity enables skillful motor actions such as those required for musical performance. However, it has been not known whether and in what manner neuromuscular or biomechanical features of the fingers subserve the dexterity. We aimed to identify the features firstly differentiating the finger dexterity between trained and untrained individuals and secondly accounting for the individual differences in the dexterity across trained individuals. To this aim, two studies were conducted. The first study compared the finger dexterity and several neuromuscular and biomechanical characteristics of the fingers between pianists and non-musicians. As a measure of the dexterity, we used the maximum rate of repetitive finger movements. The results showed no differences in any biomechanical constraints of the fingers between the two groups (i.e. anatomical connectivity between the fingers and range of motion). However, the pianists exhibited faster finger movements and more independent control of movements between the fingers. These observations indicate expertise-dependent enhancement of the finger dexterity and reduction of neuromuscular constraints on movement independence between the fingers. The second study assessed individual differences in the finger dexterity between trained pianists. A penalized regression determined an association of the maximum movement speed of the fingers with both muscular strength and biomechanical characteristics of the fingers, but not with neuromuscular constraints of the fingers. None of these features covaried with measures of early and deliberate piano practice. These findings indicate that distinct biological factors of finger motor dexterity differentiate between the effects of piano practicing and individual differences across skilled pianists.

Temporal exploration in sequential movements shapes efficient neuromuscular control

The interaction of early and deliberate practice with genetic predisposition endows experts with virtuosic motor performance. However, it has not been known whether ways of practicing shape motor virtuosity. Here, we addressed this issue by comparing the effects of rhythmic variation in motor practice on neuromuscular control of the finger movements in pianists. With the use of a novel electromyography system with miniature active electrodes, we recorded the activity of the intrinsic hand muscles of 27 pianists while they played the piano and analyzed it by using a nonnegative matrix factorization algorithm and cluster analysis. The result demonstrated that practicing a target movement sequence with various rhythms reduced muscular activity, whereas neither practicing a sequence with a single rhythm nor taking a rest without practicing changed the activity. In addition, practice with rhythmic variation changed the patterns of simultaneous activations across muscles. This alteration of muscular coordination was associated with decreased activation of muscles not only relevant to, but also irrelevant to the task performance. In contrast, piano practice improved the maximum speed of the performance, the amount of which was independent of whether rhythmic variation was present. These results suggest that temporal variation in movement sequences during practice co-optimizes both movement speed and neuromuscular efficiency, which emphasizes the significance of ways of practice in the acquisition of motor virtuosity. NEW & NOTEWORTHY A key question in motor neuroscience is whether "ways of practicing" contribute to shaping motor virtuosity. We found both attenuation of activities and alteration of coordination of the intrinsic hand muscles of pianists, specifically through practicing a movement sequence with various rhythms. The maximum speed of the finger movements was also enhanced following the practice. These results emphasize the importance of ways of practicing in facilitating multiple skills: efficiency and speed.